Choosing The Right Nitrogen Rate For Corn Is Important To Profitability

Nitrogen (N) rate on-farm trial in the field with hog manure applied in early August the previous year. The 16-row strips that are the most yellow-green only received 30 lbs N / acre as a starter fertilizer and no sidedress N application. The economic optimum N rate for the trial turned out to be 147 total lbs of N applied per acre, with an average yield of 234 bushels/acre. The photo was taken on 14 August. (Source: Bob Nielsen, DJI Zenmuse X4S camera on DJI Matrice 200 UAV at 400 ft flight altitude.)

By: Jim Camberato and Bob Nielsen Purdue University

Although nitrogen (N) fertilizer can be costly, it is needed to optimize profit in Indiana cornfields. Applying too little N reduces profit by reducing grain yield. Too much N does not return value and can also damage the environment.

Results from 167 field-scale N response trials conducted over more than 10 years underpin current region-based N recommendations. These data-driven N recommendations replaced the old yield-goal based system1, which was proven ineffective. Current recommendations represent the N rate for maximum profit over the long-term, but differences in soil type, management, and weather can result in lower or higher N requirements in any given situation. Rainfall after N application will primarily determine the efficiency of applied N2, with excessive rainfall causing higher N loss and greater need for fertilizer N.  Although N applied prior to planting this season has not been subject to conditions promoting N loss in most areas of Indiana, N loss can occur season-long, particularly prior to the V8 growth stage when corn N uptake and water use are relatively low.

Economic optimum N rates vary by as much as 40 pounds of N per acre across regions so adjusting the N rate by region is important. Recommended rates can also be adjusted by the price of N fertilizer and the expected value of grain using tabular data in the publication “Nitrogen Management Guidelines for Corn in Indiana3. With N at $0.40 per pound and corn at $3.25 per bushel, the average N rate needed on fine-textured soils to maximize profit is about 30 pounds per acre less than that needed to maximize yield. On sandy non-irrigated soils, the difference is only about 10 pounds per acre. Using the economic optimum N rate, rather than the N rate needed for maximum yield, would reduce yield 1 to 3 bushels per acre across soil textures and regions. The loss in profit when fertilizing to maximize yield would be approximately $7 per acre for fine-textured soils, but only $2 per acre on sandy non-irrigated soils.

Nitrogen rates recommended are for efficient applications of N, such as anhydrous ammonia (AA) within a couple of weeks prior to planting or side dressed AA or liquid N. Earlier applications of liquid N2 or surface applications of urea on no-till groundcan reduce profit under certain conditions. Additional details on how to manage N efficiently can also be found here3.


1A Historical Perspective on Nitrogen Fertilizer Rate Recommendations for Corn in Indiana (1953-2011). J. Camberato. March 2015.

2N Loss Mechanisms and Nitrogen Use Efficiency. R.L. Nielsen. 2006.

3Nitrogen Management Guidelines for Corn in Indiana. J. Camberato and B. Nielsen. March 2019.

4Improving the Efficient Use of Urea-Containing Fertilizers. J. Camberato. June 2017.

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